<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
#div1 {width:100px; height:100px; background:red; position:absolute; left:600px; top:50px;}
#div2 {width:1px; height:300px; position:absolute; left:300px; top:0; background:black;}
#div3 {width:1px; height:300px; position:absolute; left:100px; top:0; background:black;}
</style>
<script>
var timer=null;

function startMove(iTarget)
{
	var oDiv=document.getElementById('div1');
	
	clearInterval(timer);
	timer=setInterval(function (){
		var speed=0;
		
		if(oDiv.offsetLeft<iTarget)
		{
			speed=7;
		}
		else
		{
			speed=-7;
		}
		
		if(Math.abs(iTarget-oDiv.offsetLeft)<=7)
		{
			clearInterval(timer);
			
			oDiv.style.left=iTarget+'px';
		}
		else
		{
			oDiv.style.left=oDiv.offsetLeft+speed+'px';
		}
	}, 30);
}
</script>
</head>

<body>
<input type="button" value="到100" onclick="startMove(100)" />
<input type="button" value="到300" onclick="startMove(300)" />
<div id="div1"></div>
<div id="div2"></div>
<div id="div3"></div>
</body>
</html>
